1. Field of the Invention
The present invention relates to an improvement in a vibration inhibiting structure in a device cover fastened to a casing of a vibration generating source, e.g., a transmission case for a transmission of a vehicle which covers a device mounted on the transmission case, e.g., a sensor. The structure is designed to inhibit the vibration of the device cover to reduce noise generated by the resonance of the device cover due to vibration generated in the transmission.
2. Description of the Prior Art
A structure is already known, for example, from Japanese Patent Application Laid-Open No. 8-244489, in which a sensor for detecting the rotational speed of an engine is mounted on an outer surface of a transmission case of the vehicle transmission, and a device cover covering the sensor, is fastened to the transmission case.
The device cover is fastened to the transmission case or the like to cover the sensor for the purpose of preventing damage to the sensor due to collision with a pebble, or to water-proof and heat-shield the sensor. However, if the transmission vibrates, and the device cover is resonated by the vibration from the transmission case, a resonance sound is radiated from the device cover.
To reduce the resonance sound from the device cover, it is a conventional practice to interpose an elastic material between the transmission case (casing) and the device cover, to enhance the rigidity of the device cover by increasing the thickness of the device cover or by reinforcing the device cover, to bond a damping material to the surface of the device cover by adhesive-bonding, baking and coating, and to form the device cover from a damping steel plate, thereby inhibiting the vibration of the device cover to the utmost.
However, in the structure having the elastic material interposed between the transmission case and the device cover, deterioration of the elastic material occurs due to heat from the transmission case or due to the passage of time, resulting in a problem in durability. In the technique which enhances the rigidity of the device cover, it is impossible to accommodate variations in the vibration mode on the side of the vehicle transmission which is a vibration generating source. In the structure in which the damping material is bonded and in the structure in which the device cover is formed of the damping steel plate, there is an increase in cost.